In early research, Paenibacillus was classified into Bacillus based on the morphology. In 1994, by using PCR probe testing, Ash et al. analyzed the 16S rRNA sequences for different strains of Bacillus, and found that some of the Bacillus were significantly different from other Bacillus in terms of genotypic characteristics, and their 16S rRNA sequences were highly specific. Therefore, Ash separated 11 strains such as Bacillus polymyxin from Bacillus to form an independent genus, namely Paenibacillus. 
The type strain of Paenibacillus is Paenibacillus polmyxin ATCC 842T, wherein the cells are in the shape of rods, the optimal growth temperature range is 28-30° C. and the main fatty acid is anteiso saturated fatty acid C15:0. The G+C content of Paenibacillus range is 45-54 mol %.
Generally, if the difference of G+C mol % between two strains is more than 5%, the two strains could be determined as different species (such determination can be made even if other characteristics are similar). The DNA homology analysis may finally determine the classification of the strains. It is also a way for determining new species. In optimum conditions, if the DNA homology is higher than 70%, the strains belong to the same species. If the DNA homology is higher than 20%, the strains belong to the same genus. Nowadays, it is believed that the effects of the combination of phenotype and DNA homology to classify species and genus are accurate and desirable.
Many microorganisms of Paenibacillus genus have the effects of disease-preventing and growth-promoting on plants. Therefore, they have a good usage potential in agricultural industry. The Paenibacillus may produce many kinds of bioactive substances such as enzymes, antibiotic substances, phytohormones, flocculants, and etc. Most of these active substances are proteins, polypeptides and polysaccharides, and etc.
Microbial extracellular polysaccharides (EPS for short), in some extent, have been demonstrated with the functions of anti-hyperlipidemia, immunoregulatory and anti-tumor and etc. Therefore, it may serve as the food additive. As the consumers are more and more concerned about the food safety issues, how to obtain new food additives (for example, thickener, emulsifier, stabilizer, etc) with a clear source, stable yield, and diverse functions attracted more and more attentions from researchers.
Levan is a type of fructans constituted of fructose units linked with β (2→6) fructoside bonds in main chain and with or without a few the branchs lingked by β (2→1) fructoside bonds. The levan with a low polymerization (DP for short) (DP=2-9) is usually called fructooligosaccharide. The levan with a DP range of 10-30 is usually called polyfructose. The levan with a DP higher than 40 is usually called high-polyfructose. Some levans that originates from microorganism have important biological activities such as anti-tumor, anti-virus, anti-hyperglycaemia, anti-hyperlipidemia and immunopotentiation, and thus they have a large usage potential in terms of medicines and functional foods.
There are three methods for producing levans in large quantities nowadays: the chemical synthesis method, the microbiological fermentation and enzymatic synthesis method. However, currently, the chemical synthesis method merely produces the trisaccharides formed by β-glycosidic bonds. Although both plants and microorganisms may produce levans, currently the levans produced by microorganism fermentation are all of high molecular weights with high polymerization degrees, usually 2×106-100×106 Da and the DP is far more than 40. However, nowadays the yield and conversion rate of saccharose to manufacture levans from microbiological fermentation are usually low. Also, other products such as high polymers, glucoses, fructose, and fructooligosaccharides coexist in the fermentation broth. Thus, it is disadvantageous for large-scale purification of levans. On the other hand, the enzymatic synthesis method for producing levans requires certain conditions such as the particular pH, the temperature, and ect. to facilitate the reaction, which is complex and hard to control. Therefore, the strain with high productivity of levans and high saccharose conversion rate is the key for large-scale preparation of levans, especially for the levans with moderate and low polymerization.